1/*
2 * From: @(#)s_ilogb.c 5.1 93/09/24
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include <sys/cdefs.h>
14__FBSDID("$FreeBSD$");
15
16#include <float.h>
17#include <limits.h>
18#include <math.h>
19
20#include "fpmath.h"
21
22int
23ilogbl(long double x)
24{
25	union IEEEl2bits u;
26	unsigned long m;
27	int b;
28
29	u.e = x;
30	if (u.bits.exp == 0) {
31		if ((u.bits.manl | u.bits.manh) == 0)
32			return (FP_ILOGB0);
33		/* denormalized */
34		if (u.bits.manh == 0) {
35			m = 1lu << (LDBL_MANL_SIZE - 1);
36			for (b = LDBL_MANH_SIZE; !(u.bits.manl & m); m >>= 1)
37				b++;
38		} else {
39			m = 1lu << (LDBL_MANH_SIZE - 1);
40			for (b = 0; !(u.bits.manh & m); m >>= 1)
41				b++;
42		}
43#ifdef LDBL_IMPLICIT_NBIT
44		b++;
45#endif
46		return (LDBL_MIN_EXP - b - 1);
47	} else if (u.bits.exp < (LDBL_MAX_EXP << 1) - 1)
48		return (u.bits.exp - LDBL_MAX_EXP + 1);
49	else if (u.bits.manl != 0 || u.bits.manh != 0)
50		return (FP_ILOGBNAN);
51	else
52		return (INT_MAX);
53}
54